With no cure in hand for Alzheimer's disease, many ask why someone would necessarily want an early diagnosis. But research continues to focus on detecting the earliest signs of dementia, and on the factors that give rise to some dementias or fuel their relentless progression. Those findings may point the way to prevention strategies. And they may allow physicians to recognize Alzheimer's disease and other dementias before they have taken a measurable toll. Stopping or slowing it there might be easier than reversing it, and could, for all practical purposes, be as good as a cure.